Conventionally, solar cells are known to have, for example, an n-type semiconductor substrate and a p-type semiconductor layer arranged on the semiconductor substrate. As is well known, carrier recombining can be suppressed in these solar cells by introducing hydrogen to the semiconductor layer to reduce the density of defects in the semiconductor layer. Also, the bandgap energy of the semiconductor layer can be increased and light-absorption loss reduced by introducing hydrogen to the semiconductor layer and increasing the number of hydrogen atoms bonded to silicon atoms.
A method for introducing hydrogen to a semiconductor layer is described in Patent Document 1. In this method, the semiconductor layer is irradiated with hydrogen ions which have been accelerated by an electric field to which an acceleration voltage of approximately 1 eV to 5 keV has been applied.